Reference has been made above to assignee's particular fire alarm and detection system as described in U.S. patent 5,670,937. The description of that patents system is incorporated herein by reference. In essence, that system--aside from the particular line monitor feature--forms the context or environment for the inventive improvement to be described.
Other examples of prior systems of this general type can be appreciated by reference to U.S. Pat. Nos. 4,568,919, 4,752,698, 4,850,018, 4,954,809 and 4,962,308. Most of these U.S. patents describe systems that include a loop controller or the like which initiates the determination of the states of the units or transponders at various zones or stations in the system, typically by repetitive polling of the stations, whereby addresses are sent successively on the loop or lines to determine which, if any, units are in an alarm state; any units reporting an alarm state receive back from the loop controller an activate relay command. Provision is also made of most of these systems to detect and report trouble conditions.
In providing alarm signals at particular stations or locations, it is the common practice to supply power to strobes which provide flashing light and to horns which produce non-continuous sounds. However, a problem arises when the sources of light and sound are operating such that the sources lack synchronization of the power being supplied to them; hence, they will produce confusion during an alarm situation. For example, an aberrant mixture of unsynchronized light pulses or horn blasts may give rise to confusion of signals, thus frustrating efficient warning to occupants of the emergency conditions.
It can be appreciated that the desired synchronization of alarm signals from the aforesaid typical strobes and horns and the like is difficult when it has to be accomplished over large areas because there is a need to power such output devices from multiple power supplies that differ in operating characteristics.
Accordingly, it is the primary object of the present invention to improve the already known fire alarm systems of the type described in U.S. Pat. No. 5,670,937.
A further object of the present invention to solve the serious problem noted above, i.e., of satisfying the need for appropriate synchronization of alarm devices that are powered by a number of power supplies that tend to vary or drift such that, left to themselves, are not capable of remaining in complete synchronization.
Another object is to improve upon a modules previously found in the earlier fire alarm systems by providing specialized, more intelligent modules, sometimes referred to as auto synchronous output modules, that will realize the needed synchronization across many separated alarm zones.